The present invention generally relates to valve pressure control and, more particularly, relates to the valve pressure control as it relates to brake and wheel slip control on a transit railway vehicle and, still more particularly, to a microprocessor for controlling the control logic of a passenger transit vehicle and, even more particularly, to a microprocessor system designed to control the magnet valves, apply and release the magnet valves for proper fixed pulse timing to improve the lifecycle of these valves.
There are known, in the prior art, many transit systems that require brake and/or wheel slip control and use microprocessors that run wheel slip calculations and control logic at 20 milliseconds (ms) intervals, and which generally use single 20 ms interrupts. The 20 ms interrupt control has proven sufficient for most applications in the past with simpler system interfaces and larger brake cylinder pressure tolerances. However, since current and future systems are becoming more sophisticated which necessitates tighter control requirements and which can be used in a broader range of applications and tolerances. The use of the single 20 ms time step has become a limitation in certain present applications. For example, several three-state valves that were used to control brake cylinder pressure have had problems maintaining stability with tight tolerances, and in some configurations cannot achieve brake cylinder pressure changes as small as 1 or 2 psi. Even if the system is successfully calibrated to achieve these tight tolerances initially, they cannot be maintained for long time periods as the magnet valve components wear.
In one aspect the present invention provides a microprocessor based smart resolution valve pressure control system for performing a wheel slip control valve response test. Included in the system is a sensing means and a begin decision means for ensuring that brakes disposed on the truck of a vehicle are at full service and that a truck brake cylinder pressure (BCP) is greater than a first predetermined BCP. Also included is a first testing means connected to a wheel slip control valve for pulse releasing a wheel slip control valve to determine an elapsed time that the truck BCP drops from a second predetermined BCP to a third predetermined BCP. The system also includes a release time adjustment means connected to the first testing means for either adding or subtracting to and from, respectively, a release time and hold time depending on the elapsed time. Also included is a release time decision means for detecting if the release time adjustment means has changed the release time, and a reapply brake cylinder pressure means connected to the release time decision means for enabling again the first testing means if the release time has changed. The system also includes an exhaust brake cylinder pressure means connected to the release time decision means for sending a pulsed release signal and a pulsed hold signal to a control valve and a continue decision means connected between the exhaust brake cylinder pressure means and a second testing means for ensuring that an exhaust BCP is less than a predetermined amount. The second testing means applies an apply pulse to a control valve for a predetermined time and times a BCP rise between a fourth predetermined BCP and a fifth predetermined BCP. Also included in the system is an apply time adjustment means connected to the second testing means for either adding or subtracting to and from, respectively, an apply time and hold time depending on the time of the BCP rise between the fourth and fifth predetermined BCP. An apply time decision means connected to the apply time adjustment means for sending either an enabling signal to a release brake cylinder pressure means connected to the apply time decision means if the apply time has changed, or to an end wheel slip control valve test signal. The release brake cylinder pressure means, when enabled, enables again the second testing means.
Another aspect of the present invention provides a microprocessor based smart resolution valve pressure control apparatus used to control a wheel slip control magnet valve. Included in the apparatus is a logic control means for providing one of a release time and an application time together with a hold time. The apparatus also includes a change decision means connected to a logic control means for determining if either the release time or the application time, or the hold time have changed since a last cycle of the apparatus used to control a wheel slip control magnet valve. There is a valve timing set up means connected to a change decision means for setting either a release time, an application time, or a hold time if either the release time or the application time have changed. A pulse timing means is connected to a change decision means and the valve timing set up means for determining if a remaining pulse time is equal to 0, and enabling a hold timing means if the remaining pulse time is equal to 0, and enabling a pulse timer decrement means if the remaining pulse time is greater than 0. The hold timing means is connected to the pulse timing means for determining if a remaining hold time is equal to 0, and enabling a timer""s reset means if the remaining hold time is equal to 0, and enabling a hold timer decrement means if the remaining hold time is greater than 0. The pulse timer decrement means and the hold timer decrement means decrement one of the remaining pulse time and the remaining hold time, respectively, and enables a valve control means. There is a timer""s reset means for resetting the pulse timing means and the hold timing means. The valve control means enables a magnet valve based on the current pulse time or hold time, and an end interrupt routine means for ending a current repetition of controlling the wheel slip control magnet valve after either enabling the magnet valve, or resetting the pulse timing means and the hold timing means.
Yet another aspect of the present invention provides a microprocessor based smart resolution valve pressure control method for calibrating a smart resolution valve pressure control having a plurality of release times and a corresponding plurality of hold times. The method includes applying a release pulse of a first predetermined duration of one of a selected plurality of release times and applying a hold pulse of a second predetermined duration corresponding to the selected plurality of release times to a valve controlling the pressure to a brake cylinder, wherein the brake cylinder initially has a minimum first predetermined pressure. The method also includes a) measuring the elapsed time that the brake cylinder changes from a second predetermined pressure to a third predetermined pressure, and b) increasing the first predetermined duration and decreasing the second predetermined duration if the elapsed time is greater than a first predetermined time, and decreasing the first predetermined duration and increasing the second predetermined duration if said elapsed time is less than a second predetermined time. Also included in the method is repeating steps a) and b) if the first predetermined duration changes.
A further aspect of the present invention provides a microprocessor based smart resolution valve pressure control method for calibrating a smart resolution valve pressure control having a plurality of application times and a corresponding plurality of hold times. The method includes applying an application pulse of a first predetermined duration of the plurality of application times and applying a hold pulse of a second predetermined duration corresponding to the selected plurality of application times to a valve controlling the pressure to a brake cylinder, wherein the brake cylinder initially has a maximum first predetermined pressure. The method also includes a) measuring the elapsed time the brake cylinder changes from a second predetermined pressure to a third predetermined pressure, and b) increasing the first predetermined duration and decreasing the second predetermined duration if the elapsed time is greater than a first predetermined time, and decreasing the first predetermined duration and increasing the second predetermined duration if the elapsed time is less than a second predetermined time. Also included in the method is repeating steps a) and b) if the first predetermined duration changes.
It is, therefore, one of the primary objects of the present invention to provide a smart resolution valve pressure control to allow any pressure control system using valve state pulsing to provide an airflow rate having an optimum and consistent range of operation.
Another object of the present invention is to provide a smart resolution valve pressure control system which provides the valve-control interrupt pressure commands from the calculations performed during the primary control interrupt of a microprocessor.
Another object of the present invention is to provide a smart resolution valve pressure control system to generate the necessary valve commands to achieve the requested pressure calculated from the primary control interrupt process.
Another object of the present invention is to provide a smart resolution valve pressure control system to communicate and interface with the valve every millisecond instead of every 20 ms to allow a greater degree of valve control, which improves control accuracy.
Yet another object of the present invention is to provide a smart resolution valve pressure control system to provide an accurate pressure output within a desired bandwidth which utilizes a smart algorithm that relies on a self-adjusting calibrated pulse time for a minimum pressure adjustment.
Yet another object of the present invention is to provide a smart resolution valve pressure control system to reduce the valve cycles significantly and to thereby increase the valve life.
Still another object of the present invention is to provide a smart resolution valve pressure control system to provide an improved shorter interrupt control time.
Although a number of objects and advantages of the present invention have been described in some detail above, various additional objects and advantages of the smart resolution valve pressure control of the present invention will become more readily apparent to those persons who are skilled in the art from the following more detailed description of the invention, particularly when such detailed description of the invention is taken in conjunction with the attached Figures and the appended claims.